<!DOCTYPE HTML>
<html lang="zh-CN">


<head>
    <meta charset="utf-8">
    <meta name="keywords" content="死磕Redis之数据类型, Java，Flutter，Dart，架构，编程，技术分享，读书分享">
    <meta name="description" content="Redis数据类型Redis之所以很流行，除了作为集中式缓存之外，还因为其提供了丰富的数据类型，我们看下都有哪些数据类型。对外的API数据类型主要有以下几种：

String
List
Hash
Set
Sorted Set

而对应的底层">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
    <meta name="renderer" content="webkit|ie-stand|ie-comp">
    <meta name="mobile-web-app-capable" content="yes">
    <meta name="format-detection" content="telephone=no">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
    <meta name="referrer" content="no-referrer-when-downgrade">
    <!-- Global site tag (gtag.js) - Google Analytics -->


    <title>死磕Redis之数据类型 | 武码公社</title>
    <link rel="icon" type="image/png" href="/favicon.png">

    <link rel="stylesheet" type="text/css" href="/libs/awesome/css/all.css">
    <link rel="stylesheet" type="text/css" href="/libs/materialize/materialize.min.css">
    <link rel="stylesheet" type="text/css" href="/libs/aos/aos.css">
    <link rel="stylesheet" type="text/css" href="/libs/animate/animate.min.css">
    <link rel="stylesheet" type="text/css" href="/libs/lightGallery/css/lightgallery.min.css">
    <link rel="stylesheet" type="text/css" href="/css/matery.css">
    <link rel="stylesheet" type="text/css" href="/css/my.css">

    <script src="/libs/jquery/jquery.min.js"></script>

<meta name="generator" content="Hexo 5.4.0"></head>




<body>
    <header class="navbar-fixed">
    <nav id="headNav" class="bg-color nav-transparent">
        <div id="navContainer" class="nav-wrapper container">
            <div class="brand-logo">
                <a href="/" class="waves-effect waves-light">
                    
                    <img src="/medias/logo.png" class="logo-img" alt="LOGO">
                    
                    <span class="logo-span">武码公社</span>
                </a>
            </div>
            

<a href="#" data-target="mobile-nav" class="sidenav-trigger button-collapse"><i class="fas fa-bars"></i></a>
<ul class="right nav-menu">
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/" class="waves-effect waves-light">
      
      <i class="fas fa-home" style="zoom: 0.6;"></i>
      
      <span>首页</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/tags" class="waves-effect waves-light">
      
      <i class="fas fa-tags" style="zoom: 0.6;"></i>
      
      <span>标签</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/categories" class="waves-effect waves-light">
      
      <i class="fas fa-bookmark" style="zoom: 0.6;"></i>
      
      <span>分类</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/archives" class="waves-effect waves-light">
      
      <i class="fas fa-archive" style="zoom: 0.6;"></i>
      
      <span>归档</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/about" class="waves-effect waves-light">
      
      <i class="fas fa-user-circle" style="zoom: 0.6;"></i>
      
      <span>关于</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/contact" class="waves-effect waves-light">
      
      <i class="fas fa-comments" style="zoom: 0.6;"></i>
      
      <span>留言板</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a target="_blank" rel="noopener" href="https://lox.dengwu.wang" class="waves-effect waves-light">
      
      <i class="fas fa-book" style="zoom: 0.6;"></i>
      
      <span>自己动手写解释器</span>
    </a>
    
  </li>
  
  <li>
    <a href="#searchModal" class="modal-trigger waves-effect waves-light">
      <i id="searchIcon" class="fas fa-search" title="搜索" style="zoom: 0.85;"></i>
    </a>
  </li>
</ul>


<div id="mobile-nav" class="side-nav sidenav">

    <div class="mobile-head bg-color">
        
        <img src="/medias/logo.png" class="logo-img circle responsive-img">
        
        <div class="logo-name">武码公社</div>
        <div class="logo-desc">
            
            思考和积累
            
        </div>
    </div>

    <ul class="menu-list mobile-menu-list">
        
        <li class="m-nav-item">
	  
		<a href="/" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-home"></i>
			
			首页
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/tags" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-tags"></i>
			
			标签
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/categories" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-bookmark"></i>
			
			分类
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/archives" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-archive"></i>
			
			归档
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/about" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-user-circle"></i>
			
			关于
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/contact" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-comments"></i>
			
			留言板
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a target="_blank" rel="noopener" href="https://lox.dengwu.wang" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-book"></i>
			
			自己动手写解释器
		</a>
          
        </li>
        
        
        <li><div class="divider"></div></li>
        <li>
            <a href="https://github.com/wangdengwu" class="waves-effect waves-light" target="_blank">
                <i class="fab fa-github-square fa-fw"></i>我的代码库
            </a>
        </li>
        
    </ul>
</div>


        </div>

        
            <style>
    .nav-transparent .github-corner {
        display: none !important;
    }

    .github-corner {
        position: absolute;
        z-index: 10;
        top: 0;
        right: 0;
        border: 0;
        transform: scale(1.1);
    }

    .github-corner svg {
        color: #0f9d58;
        fill: #fff;
        height: 64px;
        width: 64px;
    }

    .github-corner:hover .octo-arm {
        animation: a 0.56s ease-in-out;
    }

    .github-corner .octo-arm {
        animation: none;
    }

    @keyframes a {
        0%,
        to {
            transform: rotate(0);
        }
        20%,
        60% {
            transform: rotate(-25deg);
        }
        40%,
        80% {
            transform: rotate(10deg);
        }
    }
</style>

<a href="https://github.com/wangdengwu" class="github-corner tooltipped hide-on-med-and-down" target="_blank"
   data-tooltip="我的代码库" data-position="left" data-delay="50">
    <svg viewBox="0 0 250 250" aria-hidden="true">
        <path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path>
        <path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2"
              fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path>
        <path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z"
              fill="currentColor" class="octo-body"></path>
    </svg>
</a>
        
    </nav>

</header>

    



<div class="bg-cover pd-header post-cover" style="background-image: url('/medias/featureimages/8.jpg')">
    <div class="container" style="right: 0px;left: 0px;">
        <div class="row">
            <div class="col s12 m12 l12">
                <div class="brand">
                    <h1 class="description center-align post-title">死磕Redis之数据类型</h1>
                </div>
            </div>
        </div>
    </div>
</div>




<main class="post-container content">

    
    <link rel="stylesheet" href="/libs/tocbot/tocbot.css">
<style>
    #articleContent h1::before,
    #articleContent h2::before,
    #articleContent h3::before,
    #articleContent h4::before,
    #articleContent h5::before,
    #articleContent h6::before {
        display: block;
        content: " ";
        height: 100px;
        margin-top: -100px;
        visibility: hidden;
    }

    #articleContent :focus {
        outline: none;
    }

    .toc-fixed {
        position: fixed;
        top: 64px;
    }

    .toc-widget {
        width: 345px;
        padding-left: 20px;
    }

    .toc-widget .toc-title {
        padding: 35px 0 15px 17px;
        font-size: 1.5rem;
        font-weight: bold;
        line-height: 1.5rem;
    }

    .toc-widget ol {
        padding: 0;
        list-style: none;
    }

    #toc-content {
        padding-bottom: 30px;
        overflow: auto;
    }

    #toc-content ol {
        padding-left: 10px;
    }

    #toc-content ol li {
        padding-left: 10px;
    }

    #toc-content .toc-link:hover {
        color: #42b983;
        font-weight: 700;
        text-decoration: underline;
    }

    #toc-content .toc-link::before {
        background-color: transparent;
        max-height: 25px;

        position: absolute;
        right: 23.5vw;
        display: block;
    }

    #toc-content .is-active-link {
        color: #42b983;
    }

    #floating-toc-btn {
        position: fixed;
        right: 15px;
        bottom: 76px;
        padding-top: 15px;
        margin-bottom: 0;
        z-index: 998;
    }

    #floating-toc-btn .btn-floating {
        width: 48px;
        height: 48px;
    }

    #floating-toc-btn .btn-floating i {
        line-height: 48px;
        font-size: 1.4rem;
    }
</style>
<div class="row">
    <div id="main-content" class="col s12 m12 l9">
        <!-- 文章内容详情 -->
<div id="artDetail">
    <div class="card">
        <div class="card-content article-info">
            <div class="row tag-cate">
                <div class="col s7">
                    
                    <div class="article-tag">
                        
                            <a href="/tags/redis/">
                                <span class="chip bg-color">redis</span>
                            </a>
                        
                            <a href="/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E7%BC%93%E5%AD%98/">
                                <span class="chip bg-color">分布式缓存</span>
                            </a>
                        
                    </div>
                    
                </div>
                <div class="col s5 right-align">
                    
                    <div class="post-cate">
                        <i class="fas fa-bookmark fa-fw icon-category"></i>
                        
                            <a href="/categories/%E6%AD%BB%E7%A3%95Redis/" class="post-category">
                                死磕Redis
                            </a>
                        
                    </div>
                    
                </div>
            </div>

            <div class="post-info">
                
                <div class="post-date info-break-policy">
                    <i class="far fa-calendar-minus fa-fw"></i>发布日期:&nbsp;&nbsp;
                    2022-03-15
                </div>
                

                
                <div class="post-date info-break-policy">
                    <i class="far fa-calendar-check fa-fw"></i>更新日期:&nbsp;&nbsp;
                    2022-07-18
                </div>
                

                
                <div class="info-break-policy">
                    <i class="far fa-file-word fa-fw"></i>文章字数:&nbsp;&nbsp;
                    2.1k
                </div>
                

                

                
            </div>
        </div>
        <hr class="clearfix">

        
        <!-- 是否加载使用自带的 prismjs. -->
        <link rel="stylesheet" href="/libs/prism/prism.css">
        

        

        <div class="card-content article-card-content">
            <div id="articleContent">
                <h3 id="Redis数据类型"><a href="#Redis数据类型" class="headerlink" title="Redis数据类型"></a>Redis数据类型</h3><p>Redis之所以很流行，除了作为集中式缓存之外，还因为其提供了丰富的数据类型，我们看下都有哪些数据类型。<br>对外的API数据类型主要有以下几种：</p>
<ul>
<li>String</li>
<li>List</li>
<li>Hash</li>
<li>Set</li>
<li>Sorted Set</li>
</ul>
<p>而对应的底层数据结构则有<br><img src="https://img.dengwu.wang/blog/202203181617189.png"></p>
<h3 id="Redis的Key-Value存储结构"><a href="#Redis的Key-Value存储结构" class="headerlink" title="Redis的Key-Value存储结构"></a>Redis的Key-Value存储结构</h3><p>我们知道Redis是通过Key来操作Value的，那Key-Value的对应关系又是怎么样的呢，如何快速通过key找到对应的value呢<br><img src="https://img.dengwu.wang/blog/202203151254812.png" alt="图片来源-极客时间-Redis核心技术与实践"><br>既然是使用哈希表的方式，当KEY比较多的时候，必然会出现哈希冲突的情况，那如果有哈希冲突，redis是如何处理的呢。<br><img src="https://img.dengwu.wang/blog/202203151518362.png" alt="图片来源-极客时间-Redis核心技术与实践"><br>首先使用链式哈希解决哈希冲突，但是如果链式长度过长，也会导致性能下降，则Redis会进行一次渐进式rehash操作。<br><img src="https://img.dengwu.wang/blog/202203181217176.png" alt="图片来源-极客时间-Redis核心技术与实践"><br>其实不止因为哈希冲突会扩充全局哈希表，随着Key的增多，容量不够时一样会进行扩充全局哈希表，我们来看下日志。<br>首先修改日志级别为verbose和设置日志文件</p>
<pre class="line-numbers language-none"><code class="language-none">loglevel verbose
logfile &quot;&#x2F;usr&#x2F;local&#x2F;etc&#x2F;redis&#x2F;redis.log&quot;<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span></span></code></pre>
<p>执行Set命令后可以看到日志如下：</p>
<pre class="line-numbers language-none"><code class="language-none">1:C 17 Mar 2022 15:26:59.612 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
1:C 17 Mar 2022 15:26:59.612 # Redis version&#x3D;6.2.6, bits&#x3D;64, commit&#x3D;00000000, modified&#x3D;0, pid&#x3D;1, just started
1:C 17 Mar 2022 15:26:59.612 # Configuration loaded
1:M 17 Mar 2022 15:26:59.613 * monotonic clock: POSIX clock_gettime
1:M 17 Mar 2022 15:26:59.613 * Running mode&#x3D;standalone, port&#x3D;6379.
1:M 17 Mar 2022 15:26:59.613 # Server initialized
1:M 17 Mar 2022 15:26:59.613 * Ready to accept connections
1:M 17 Mar 2022 15:28:52.452 - Accepted 127.0.0.1:49086
1:M 17 Mar 2022 15:29:24.969 - DB 0: 1 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:29.980 - DB 0: 2 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:34.993 - DB 0: 2 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:40.005 - DB 0: 2 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:45.018 - DB 0: 2 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:50.030 - DB 0: 3 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:29:55.042 - DB 0: 3 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:30:00.053 - DB 0: 4 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:30:05.066 - DB 0: 4 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:30:10.079 - DB 0: 4 keys (0 volatile) in 4 slots HT.
1:M 17 Mar 2022 15:30:15.091 - DB 0: 5 keys (0 volatile) in 8 slots HT.
1:M 17 Mar 2022 15:30:20.104 - DB 0: 6 keys (0 volatile) in 8 slots HT.
1:M 17 Mar 2022 15:32:55.475 - DB 0: 7 keys (0 volatile) in 8 slots HT.
1:M 17 Mar 2022 15:33:00.488 - DB 0: 9 keys (0 volatile) in 16 slots HT.
1:M 17 Mar 2022 15:33:05.498 - DB 0: 10 keys (0 volatile) in 16 slots HT.<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<p>有些重复的日志我删掉了，可以看到初始化是4个slots，后续扩容都会翻倍。</p>
<h3 id="dictEntry"><a href="#dictEntry" class="headerlink" title="dictEntry"></a>dictEntry</h3><p>全局哈希表里存储的具体对象是dictEntry，具体结构是什么样的呢？<br><img src="https://img.dengwu.wang/blog/202203181350496.png"><br>以Set hello world指令举例，属性key即设置的hello，指向sds（Simple Dynamic String）类型<br>属性val指向redisObject类型,而next即哈希冲突的拉链，指向下一个entry</p>
<h3 id="redisObject"><a href="#redisObject" class="headerlink" title="redisObject"></a>redisObject</h3><p>Redis中的每个对象底层的数据结构都是redisObject结构体</p>
<ul>
<li>type    :记录redis的对象类型</li>
<li>encoding:记录底层编码，即使用哪种数据结构保存数据</li>
<li>lru:和缓存淘汰相关</li>
<li>refcount:对象被引用的次数</li>
<li>ptr:指向底层数据结构的指针<br>type记录值的类型，即string,list,set,hash,zset,包括后续新增的stream,geo,bitmap等新的类型</li>
</ul>
<pre class="line-numbers language-none"><code class="language-none">127.0.0.1:6379&gt; SET hello world
OK
127.0.0.1:6379&gt; type hello
string
127.0.0.1:6379&gt; LPUSH list 1
(integer) 1
127.0.0.1:6379&gt; type list
list
127.0.0.1:6379&gt; SADD set 1
(integer) 1
127.0.0.1:6379&gt; type set
set
127.0.0.1:6379&gt; HSET hash hello world
(integer) 1
127.0.0.1:6379&gt; type hash
hash
127.0.0.1:6379&gt; ZADD zset 1 hello
(integer) 1
127.0.0.1:6379&gt; type zset
zset<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<p>encoding即底层存储数据结构，可以使用object encoding key来确定encoding的类型</p>
<pre class="line-numbers language-none"><code class="language-none">127.0.0.1:6379&gt; object encoding hello
&quot;embstr&quot;
127.0.0.1:6379&gt; object encoding 1
&quot;int&quot;
127.0.0.1:6379&gt; object encoding list
&quot;quicklist&quot;
127.0.0.1:6379&gt; object encoding set
&quot;intset&quot;
127.0.0.1:6379&gt; object encoding hash
&quot;ziplist&quot;
127.0.0.1:6379&gt; object encoding zset
&quot;ziplist&quot;<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<p>具体每个type对应的encoding如下：<br><img src="https://img.dengwu.wang/blog/202203181516759.png"></p>
<h3 id="字符串类型"><a href="#字符串类型" class="headerlink" title="字符串类型"></a>字符串类型</h3><p>Redis没有使用c语言的字符串，而是自己写了一个，并且做了优化，会根据字符串的长度的不同使用不同的类型以减小内存占用。<br>每个类型大体上都有以下属性：</p>
<ul>
<li>len:字符串长度</li>
<li>alloc:分配的空间长度</li>
<li>flags:标识类型</li>
<li>buf[]:字符数组<br><img src="https://img.dengwu.wang/blog/202203181424818.png"><br>在sdshdr5中将类型放到了flags的前3个字节中（3个字节能保存6种类型，所以3个字节足够了），后5个字节用来保存字符的长度。因为sdshdr5取消了alloc字段，因此也不会进行空间预分配<br>当存储的val为数字类型时，则直接使用整数来保存这个字符串，也就是redisObject里的属性val，直接存数字，这也是type是int的由来。<br>当字符串的长度小于等于44字节时，redisObject和sds一起分配内存。当字符串大于44字节时，才对redisObject分配一次内存，对sds分配一次内存<br><img src="https://img.dengwu.wang/blog/202203181527532.png"></li>
</ul>
<h5 id="为什么以44字节为界限？"><a href="#为什么以44字节为界限？" class="headerlink" title="为什么以44字节为界限？"></a>为什么以44字节为界限？</h5><p>redisObject：16个字节<br>SDS：sdshdr8（3个字节）+ SDS 字符数组（N字节 + \0结束符 1个字节）<br>Redis规定嵌入式字符串最大以64字节存储，所以N=64-16-3-1=44 </p>
<h5 id="为什么嵌入式字符串最大以64字节存储？"><a href="#为什么嵌入式字符串最大以64字节存储？" class="headerlink" title="为什么嵌入式字符串最大以64字节存储？"></a>为什么嵌入式字符串最大以64字节存储？</h5><p>因为在x86体系下，一般的缓存行大小是63字节，redis能一次加载完成</p>
<pre class="line-numbers language-none"><code class="language-none">127.0.0.1:6379&gt; SET hello world
OK
127.0.0.1:6379&gt; object encoding hello
&quot;embstr&quot;
127.0.0.1:6379&gt; SET hello 01234567890123456789012345678901234567890123
OK
127.0.0.1:6379&gt; object encoding hello
&quot;embstr&quot;
127.0.0.1:6379&gt; SET hello 012345678901234567890123456789012345678901234
OK
127.0.0.1:6379&gt; object encoding hello
&quot;raw&quot;<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<h3 id="ziplist数据结构"><a href="#ziplist数据结构" class="headerlink" title="ziplist数据结构"></a>ziplist数据结构</h3><p>由于ziplist数据结构几乎在所有集合都用到了，需要先介绍一下ziplist<br>压缩列表实际上类似于一个数组，数组中的每一个元素都对应保存一个数据。和数组不同的是，压缩列表在表头有三个字段 zlbytes、zltail 和 zllen，分别表示列表长度、列表尾的偏移量和列表中的 entry 个数；压缩列表在表尾还有一个 zlend，表示列表结束。<br><img src="https://img.dengwu.wang/blog/202203181539390.png"></p>
<h3 id="List类型"><a href="#List类型" class="headerlink" title="List类型"></a>List类型</h3><p>list类型现在是直接使用quicklist实现的<br>quicklist是一个双向链表，链表中每个节点是一个ziplist<br><img src="https://img.dengwu.wang/blog/202203181541836.png"></p>
<h3 id="Hash类型"><a href="#Hash类型" class="headerlink" title="Hash类型"></a>Hash类型</h3><p>元素比较少时用ziplist来存储，当元素比较多时用hash来存储<br>元素比较少时<br><img src="https://img.dengwu.wang/blog/202203181545270.png"><br>元素比较多时<br><img src="https://img.dengwu.wang/blog/202203181545806.png"></p>
<pre class="line-numbers language-none"><code class="language-none">127.0.0.1:6379&gt; HSET hash hello world
(integer) 0
127.0.0.1:6379&gt; object encoding hash
&quot;ziplist&quot;
127.0.0.1:6379&gt; HSET hash hello worldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworldworld
(integer) 0
127.0.0.1:6379&gt; object encoding hash
&quot;hashtable&quot;<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h3 id="Set类型"><a href="#Set类型" class="headerlink" title="Set类型"></a>Set类型</h3><p>当元素不多，且元素都为整数时，set的底层实现为intset，否则为dict<br>intset<br><img src="https://img.dengwu.wang/blog/202203181551344.png"><br>hashtable<br><img src="https://img.dengwu.wang/blog/202203181552477.png"></p>
<pre class="line-numbers language-none"><code class="language-none">127.0.0.1:6379&gt; object encoding set
&quot;intset&quot;
127.0.0.1:6379&gt; SADD set hello
(integer) 1
127.0.0.1:6379&gt; object encoding set
&quot;hashtable&quot;<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>
<h3 id="zset类型"><a href="#zset类型" class="headerlink" title="zset类型"></a>zset类型</h3><p>zset当元素较少时会使用ziplist来存储<br><img src="https://img.dengwu.wang/blog/202203181557617.png"><br>zset当元素较多时使用dict+skiplist来存储<br>dict保存了数据到分数的映射关系，skiplist用来根据分数查询数据<br><img src="https://img.dengwu.wang/blog/202203181559381.png"></p>
<h3 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h3><ul>
<li>Redis对存储整数友好，可以压缩内存使用且存取效率高</li>
<li>String不超过44长度性能最优，否则会使用raw带来额外存取操作，使用数字类型效率最高。</li>
<li>设置maxmemory，防止rdb时子进程写快照时的内存暴涨，即便停用rdb，使用slave时也会有一次rdb同步，导致内存暴涨，建议一个master不要超过2个slave。</li>
<li>设置内存淘汰策略，防止内存不够导致的异常</li>
<li>避免大KEY，hashtable结构遍历很耗时，尽量使用scan获取大量数据，而不是getall</li>
</ul>

                
            </div>
            <hr/>

            

    <div class="reprint" id="reprint-statement">
        
            <div class="reprint__author">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-user">
                        文章作者:
                    </i>
                </span>
                <span class="reprint-info">
                    <a href="https://dengwu.wang" rel="external nofollow noreferrer">王登武</a>
                </span>
            </div>
            <div class="reprint__type">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-link">
                        文章链接:
                    </i>
                    </span>
                <span class="reprint-info">
                    <a href="https://dengwu.wang/2022/03/15/si-ke-redis-zhi-shu-ju-lei-xing/">https://dengwu.wang/2022/03/15/si-ke-redis-zhi-shu-ju-lei-xing/</a>
                </span>
            </div>
            <div class="reprint__notice">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-copyright">
                        版权声明:
                    </i>
                </span>
                <span class="reprint-info">
                    本博客所有文章除特別声明外，均采用
                    <a href="https://creativecommons.org/licenses/by-nc-nd/4.0/deed.zh" rel="external nofollow noreferrer" target="_blank">CC BY-NC-ND 4.0</a>
                    许可协议。转载请注明来源
                    <a href="https://dengwu.wang" target="_blank">王登武</a>
                    !
                </span>
            </div>
        
    </div>

    <script async defer>
      document.addEventListener("copy", function (e) {
        let toastHTML = '<span>复制成功，请遵循本文的转载规则</span><button class="btn-flat toast-action" onclick="navToReprintStatement()" style="font-size: smaller">查看</a>';
        M.toast({html: toastHTML})
      });

      function navToReprintStatement() {
        $("html, body").animate({scrollTop: $("#reprint-statement").offset().top - 80}, 800);
      }
    </script>



            <div class="tag_share" style="display: block;">
                <div class="post-meta__tag-list" style="display: inline-block;">
                    
                        <div class="article-tag">
                            
                                <a href="/tags/redis/">
                                    <span class="chip bg-color">redis</span>
                                </a>
                            
                                <a href="/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E7%BC%93%E5%AD%98/">
                                    <span class="chip bg-color">分布式缓存</span>
                                </a>
                            
                        </div>
                    
                </div>
                <div class="post_share" style="zoom: 80%; width: fit-content; display: inline-block; float: right; margin: -0.15rem 0;">
                    <link rel="stylesheet" type="text/css" href="/libs/share/css/share.min.css">
<div id="article-share">

    
    <div class="social-share" data-sites="qq,qzone,wechat,weibo" data-wechat-qrcode-helper="<p>微信扫一扫即可分享！</p>"></div>
    <script src="/libs/share/js/social-share.min.js"></script>
    

    

</div>

                </div>
            </div>
            
                <style>
    #reward {
        margin: 40px 0;
        text-align: center;
    }

    #reward .reward-link {
        font-size: 1.4rem;
        line-height: 38px;
    }

    #reward .btn-floating:hover {
        box-shadow: 0 6px 12px rgba(0, 0, 0, 0.2), 0 5px 15px rgba(0, 0, 0, 0.2);
    }

    #rewardModal {
        width: 320px;
        height: 350px;
    }

    #rewardModal .reward-title {
        margin: 15px auto;
        padding-bottom: 5px;
    }

    #rewardModal .modal-content {
        padding: 10px;
    }

    #rewardModal .close {
        position: absolute;
        right: 15px;
        top: 15px;
        color: rgba(0, 0, 0, 0.5);
        font-size: 1.3rem;
        line-height: 20px;
        cursor: pointer;
    }

    #rewardModal .close:hover {
        color: #ef5350;
        transform: scale(1.3);
        -moz-transform:scale(1.3);
        -webkit-transform:scale(1.3);
        -o-transform:scale(1.3);
    }

    #rewardModal .reward-tabs {
        margin: 0 auto;
        width: 210px;
    }

    .reward-tabs .tabs {
        height: 38px;
        margin: 10px auto;
        padding-left: 0;
    }

    .reward-content ul {
        padding-left: 0 !important;
    }

    .reward-tabs .tabs .tab {
        height: 38px;
        line-height: 38px;
    }

    .reward-tabs .tab a {
        color: #fff;
        background-color: #ccc;
    }

    .reward-tabs .tab a:hover {
        background-color: #ccc;
        color: #fff;
    }

    .reward-tabs .wechat-tab .active {
        color: #fff !important;
        background-color: #22AB38 !important;
    }

    .reward-tabs .alipay-tab .active {
        color: #fff !important;
        background-color: #019FE8 !important;
    }

    .reward-tabs .reward-img {
        width: 210px;
        height: 210px;
    }
</style>

<div id="reward">
    <a href="#rewardModal" class="reward-link modal-trigger btn-floating btn-medium waves-effect waves-light red">赏</a>

    <!-- Modal Structure -->
    <div id="rewardModal" class="modal">
        <div class="modal-content">
            <a class="close modal-close"><i class="fas fa-times"></i></a>
            <h4 class="reward-title">你的赏识是我前进的动力</h4>
            <div class="reward-content">
                <div class="reward-tabs">
                    <ul class="tabs row">
                        <li class="tab col s6 wechat-tab waves-effect waves-light">
                            <a href="#wechat">微 信</a>
                        </li>
                        <li class="tab col s6 alipay-tab waves-effect waves-light">
                            <a href="#alipay">支付宝</a>
                        </li>
                    </ul>
                    <div id="wechat">
                        <img src="/medias/reward/wechat.jpg" class="reward-img" alt="微信打赏二维码">
                    </div>
                    <div id="alipay">
                        <img src="/medias/reward/alipay1.jpg" class="reward-img" alt="支付宝打赏二维码">
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>

<script>
    $(function () {
        $('.tabs').tabs();
    });
</script>

            
        </div>
    </div>

    

    

    

    

    

    

    

    

    <script src="https://utteranc.es/client.js"
        repo="wangdengwu/wangdengwu.github.io"
        issue-term="pathname"
        theme="github-light"
        crossorigin="anonymous"
        async>
    </script>

    

<article id="prenext-posts" class="prev-next articles">
    <div class="row article-row">
        
        <div class="article col s12 m6" data-aos="fade-up">
            <div class="article-badge left-badge text-color">
                <i class="fas fa-chevron-left"></i>&nbsp;上一篇</div>
            <div class="card">
                <a href="/2022/03/21/si-ke-redis-zhi-chi-jiu-hua/">
                    <div class="card-image">
                        
                        
                        <img src="/medias/featureimages/16.jpg" class="responsive-img" alt="死磕Redis之持久化">
                        
                        <span class="card-title">死磕Redis之持久化</span>
                    </div>
                </a>
                <div class="card-content article-content">
                    <div class="summary block-with-text">
                        
                            
                        
                    </div>
                    <div class="publish-info">
                        <span class="publish-date">
                            <i class="far fa-clock fa-fw icon-date"></i>2022-03-21
                        </span>
                        <span class="publish-author">
                            
                            <i class="fas fa-bookmark fa-fw icon-category"></i>
                            
                            <a href="/categories/%E6%AD%BB%E7%A3%95Redis/" class="post-category">
                                    死磕Redis
                                </a>
                            
                            
                        </span>
                    </div>
                </div>
                
                <div class="card-action article-tags">
                    
                    <a href="/tags/redis/">
                        <span class="chip bg-color">redis</span>
                    </a>
                    
                    <a href="/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E7%BC%93%E5%AD%98/">
                        <span class="chip bg-color">分布式缓存</span>
                    </a>
                    
                </div>
                
            </div>
        </div>
        
        
        <div class="article col s12 m6" data-aos="fade-up">
            <div class="article-badge right-badge text-color">
                下一篇&nbsp;<i class="fas fa-chevron-right"></i>
            </div>
            <div class="card">
                <a href="/2022/03/11/si-ke-redis-zhi-qi-shou-shi/">
                    <div class="card-image">
                        
                        
                        <img src="/medias/featureimages/23.jpg" class="responsive-img" alt="死磕Redis之起手式">
                        
                        <span class="card-title">死磕Redis之起手式</span>
                    </div>
                </a>
                <div class="card-content article-content">
                    <div class="summary block-with-text">
                        
                            
                        
                    </div>
                    <div class="publish-info">
                            <span class="publish-date">
                                <i class="far fa-clock fa-fw icon-date"></i>2022-03-11
                            </span>
                        <span class="publish-author">
                            
                            <i class="fas fa-bookmark fa-fw icon-category"></i>
                            
                            <a href="/categories/%E6%AD%BB%E7%A3%95Redis/" class="post-category">
                                    死磕Redis
                                </a>
                            
                            
                        </span>
                    </div>
                </div>
                
                <div class="card-action article-tags">
                    
                    <a href="/tags/redis/">
                        <span class="chip bg-color">redis</span>
                    </a>
                    
                    <a href="/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E7%BC%93%E5%AD%98/">
                        <span class="chip bg-color">分布式缓存</span>
                    </a>
                    
                </div>
                
            </div>
        </div>
        
    </div>
</article>

</div>


<script>
    $('#articleContent').on('copy', function (e) {
        // IE8 or earlier browser is 'undefined'
        if (typeof window.getSelection === 'undefined') return;

        var selection = window.getSelection();
        // if the selection is short let's not annoy our users.
        if (('' + selection).length < Number.parseInt('120')) {
            return;
        }

        // create a div outside of the visible area and fill it with the selected text.
        var bodyElement = document.getElementsByTagName('body')[0];
        var newdiv = document.createElement('div');
        newdiv.style.position = 'absolute';
        newdiv.style.left = '-99999px';
        bodyElement.appendChild(newdiv);
        newdiv.appendChild(selection.getRangeAt(0).cloneContents());

        // we need a <pre> tag workaround.
        // otherwise the text inside "pre" loses all the line breaks!
        if (selection.getRangeAt(0).commonAncestorContainer.nodeName === 'PRE' || selection.getRangeAt(0).commonAncestorContainer.nodeName === 'CODE') {
            newdiv.innerHTML = "<pre>" + newdiv.innerHTML + "</pre>";
        }

        var url = document.location.href;
        newdiv.innerHTML += '<br />'
            + '来源: 武码公社<br />'
            + '文章作者: 王登武<br />'
            + '文章链接: <a href="' + url + '">' + url + '</a><br />'
            + '本文章著作权归作者所有，任何形式的转载都请注明出处。';

        selection.selectAllChildren(newdiv);
        window.setTimeout(function () {bodyElement.removeChild(newdiv);}, 200);
    });
</script>


<!-- 代码块功能依赖 -->
<script type="text/javascript" src="/libs/codeBlock/codeBlockFuction.js"></script>

<!-- 代码语言 -->

<script type="text/javascript" src="/libs/codeBlock/codeLang.js"></script>


<!-- 代码块复制 -->

<script type="text/javascript" src="/libs/codeBlock/codeCopy.js"></script>


<!-- 代码块收缩 -->

<script type="text/javascript" src="/libs/codeBlock/codeShrink.js"></script>


    </div>
    <div id="toc-aside" class="expanded col l3 hide-on-med-and-down">
        <div class="toc-widget card" style="background-color: white;">
            <div class="toc-title"><i class="far fa-list-alt"></i>&nbsp;&nbsp;目录</div>
            <div id="toc-content"></div>
        </div>
    </div>
</div>

<!-- TOC 悬浮按钮. -->

<div id="floating-toc-btn" class="hide-on-med-and-down">
    <a class="btn-floating btn-large bg-color">
        <i class="fas fa-list-ul"></i>
    </a>
</div>


<script src="/libs/tocbot/tocbot.min.js"></script>
<script>
    $(function () {
        tocbot.init({
            tocSelector: '#toc-content',
            contentSelector: '#articleContent',
            headingsOffset: -($(window).height() * 0.4 - 45),
            collapseDepth: Number('0'),
            headingSelector: 'h2, h3, h4'
        });

        // modify the toc link href to support Chinese.
        let i = 0;
        let tocHeading = 'toc-heading-';
        $('#toc-content a').each(function () {
            $(this).attr('href', '#' + tocHeading + (++i));
        });

        // modify the heading title id to support Chinese.
        i = 0;
        $('#articleContent').children('h2, h3, h4').each(function () {
            $(this).attr('id', tocHeading + (++i));
        });

        // Set scroll toc fixed.
        let tocHeight = parseInt($(window).height() * 0.4 - 64);
        let $tocWidget = $('.toc-widget');
        $(window).scroll(function () {
            let scroll = $(window).scrollTop();
            /* add post toc fixed. */
            if (scroll > tocHeight) {
                $tocWidget.addClass('toc-fixed');
            } else {
                $tocWidget.removeClass('toc-fixed');
            }
        });

        
        /* 修复文章卡片 div 的宽度. */
        let fixPostCardWidth = function (srcId, targetId) {
            let srcDiv = $('#' + srcId);
            if (srcDiv.length === 0) {
                return;
            }

            let w = srcDiv.width();
            if (w >= 450) {
                w = w + 21;
            } else if (w >= 350 && w < 450) {
                w = w + 18;
            } else if (w >= 300 && w < 350) {
                w = w + 16;
            } else {
                w = w + 14;
            }
            $('#' + targetId).width(w);
        };

        // 切换TOC目录展开收缩的相关操作.
        const expandedClass = 'expanded';
        let $tocAside = $('#toc-aside');
        let $mainContent = $('#main-content');
        $('#floating-toc-btn .btn-floating').click(function () {
            if ($tocAside.hasClass(expandedClass)) {
                $tocAside.removeClass(expandedClass).hide();
                $mainContent.removeClass('l9');
            } else {
                $tocAside.addClass(expandedClass).show();
                $mainContent.addClass('l9');
            }
            fixPostCardWidth('artDetail', 'prenext-posts');
        });
        
    });
</script>

    

</main>




    <footer class="page-footer bg-color">
    

    <div class="container row center-align"
         style="margin-bottom: 0px !important;">
        <div class="col s12 m8 l8 copy-right">
            Copyright&nbsp;&copy;
            
                <span id="year">2021-2022</span>
            
            <!-- <a href="/about" target="_blank">王登武</a>
            |&nbsp;Powered by&nbsp;<a href="https://hexo.io/" target="_blank">Hexo</a>
            |&nbsp;Theme&nbsp;<a href="https://github.com/blinkfox/hexo-theme-matery" target="_blank">Matery</a> -->
            <!-- <br> -->
            
                &nbsp;<i class="fas fa-chart-area"></i>&nbsp;站点总字数:&nbsp;<span
                        class="white-color">31.6k</span>
            
            
            
            
            
            <!-- <br> -->

            <!-- 运行天数提醒. -->
            
            <br>
            
                <span id="icp"><img src="/medias/icp.png"
                                    style="vertical-align: text-bottom;"/>
                <a href="https://beian.miit.gov.cn/" target="_blank">陕ICP备2021012627号-2</a>
            </span>
            
        </div>
        <div class="col s12 m4 l4 social-link ">
    <a href="https://github.com/wangdengwu" class="tooltipped" target="_blank" data-tooltip="访问我的GitHub" data-position="top" data-delay="50">
        <i class="fab fa-github"></i>
    </a>



    <a href="mailto:me@dengwu.wang" class="tooltipped" target="_blank" data-tooltip="邮件联系我" data-position="top" data-delay="50">
        <i class="fas fa-envelope-open"></i>
    </a>







    <a href="tencent://AddContact/?fromId=50&fromSubId=1&subcmd=all&uin=251472795" class="tooltipped" target="_blank" data-tooltip="QQ联系我: 251472795" data-position="top" data-delay="50">
        <i class="fab fa-qq"></i>
    </a>





    <a href="https://www.zhihu.com/people/wangdengwu" class="tooltipped" target="_blank" data-tooltip="关注我的知乎: https://www.zhihu.com/people/wangdengwu" data-position="top" data-delay="50">
        <i class="fab fa-zhihu1">知</i>
    </a>



</div>
    </div>
</footer>

<div class="progress-bar"></div>


    <!-- 搜索遮罩框 -->
<div id="searchModal" class="modal">
    <div class="modal-content">
        <div class="search-header">
            <span class="title"><i class="fas fa-search"></i>&nbsp;&nbsp;搜索</span>
            <input type="search" id="searchInput" name="s" placeholder="请输入搜索的关键字"
                   class="search-input">
        </div>
        <div id="searchResult"></div>
    </div>
</div>

<script type="text/javascript">
$(function () {
    var searchFunc = function (path, search_id, content_id) {
        'use strict';
        $.ajax({
            url: path,
            dataType: "xml",
            success: function (xmlResponse) {
                // get the contents from search data
                var datas = $("entry", xmlResponse).map(function () {
                    return {
                        title: $("title", this).text(),
                        content: $("content", this).text(),
                        url: $("url", this).text()
                    };
                }).get();
                var $input = document.getElementById(search_id);
                var $resultContent = document.getElementById(content_id);
                $input.addEventListener('input', function () {
                    var str = '<ul class=\"search-result-list\">';
                    var keywords = this.value.trim().toLowerCase().split(/[\s\-]+/);
                    $resultContent.innerHTML = "";
                    if (this.value.trim().length <= 0) {
                        return;
                    }
                    // perform local searching
                    datas.forEach(function (data) {
                        var isMatch = true;
                        var data_title = data.title.trim().toLowerCase();
                        var data_content = data.content.trim().replace(/<[^>]+>/g, "").toLowerCase();
                        var data_url = data.url;
                        data_url = data_url.indexOf('/') === 0 ? data.url : '/' + data_url;
                        var index_title = -1;
                        var index_content = -1;
                        var first_occur = -1;
                        // only match artiles with not empty titles and contents
                        if (data_title !== '' && data_content !== '') {
                            keywords.forEach(function (keyword, i) {
                                index_title = data_title.indexOf(keyword);
                                index_content = data_content.indexOf(keyword);
                                if (index_title < 0 && index_content < 0) {
                                    isMatch = false;
                                } else {
                                    if (index_content < 0) {
                                        index_content = 0;
                                    }
                                    if (i === 0) {
                                        first_occur = index_content;
                                    }
                                }
                            });
                        }
                        // show search results
                        if (isMatch) {
                            str += "<li><a href='" + data_url + "' class='search-result-title'>" + data_title + "</a>";
                            var content = data.content.trim().replace(/<[^>]+>/g, "");
                            if (first_occur >= 0) {
                                // cut out 100 characters
                                var start = first_occur - 20;
                                var end = first_occur + 80;
                                if (start < 0) {
                                    start = 0;
                                }
                                if (start === 0) {
                                    end = 100;
                                }
                                if (end > content.length) {
                                    end = content.length;
                                }
                                var match_content = content.substr(start, end);
                                // highlight all keywords
                                keywords.forEach(function (keyword) {
                                    var regS = new RegExp(keyword, "gi");
                                    match_content = match_content.replace(regS, "<em class=\"search-keyword\">" + keyword + "</em>");
                                });

                                str += "<p class=\"search-result\">" + match_content + "...</p>"
                            }
                            str += "</li>";
                        }
                    });
                    str += "</ul>";
                    $resultContent.innerHTML = str;
                });
            }
        });
    };

    searchFunc('/search.xml', 'searchInput', 'searchResult');
});
</script>

    <!-- 回到顶部按钮 -->
<div id="backTop" class="top-scroll">
    <a class="btn-floating btn-large waves-effect waves-light" href="#!">
        <i class="fas fa-arrow-up"></i>
    </a>
</div>


    <script src="/libs/materialize/materialize.min.js"></script>
    <script src="/libs/masonry/masonry.pkgd.min.js"></script>
    <script src="/libs/aos/aos.js"></script>
    <script src="/libs/scrollprogress/scrollProgress.min.js"></script>
    <script src="/libs/lightGallery/js/lightgallery-all.min.js"></script>
    <script src="/js/matery.js"></script>

    

    <!-- 雪花特效 -->
    

    <!-- 鼠标星星特效 -->
    

    <!-- Baidu Analytics -->

    <!-- Baidu Push -->

<script>
    (function () {
        var bp = document.createElement('script');
        var curProtocol = window.location.protocol.split(':')[0];
        if (curProtocol === 'https') {
            bp.src = 'https://zz.bdstatic.com/linksubmit/push.js';
        } else {
            bp.src = 'http://push.zhanzhang.baidu.com/push.js';
        }
        var s = document.getElementsByTagName("script")[0];
        s.parentNode.insertBefore(bp, s);
    })();
</script>

    
    <script src="/libs/others/clicklove.js" async="async"></script>
    
    

    

    

    <!--腾讯兔小巢-->
    
    

    

    

    
    <script src="/libs/instantpage/instantpage.js" type="module"></script>
    

</body>

</html>
